[docs] build/test/deploy info for apps

@arthurevans @graynorton @justinfagnani @kevinpschaaf

Decide how & where to present this info

@graynorton @justinfagnani @kevinpschaaf @arthurevans FYI

#390 when doing this

PolymerLabs/start-lit-element#7 - attempted rollup (doesn't work)